1. Field of the Invention
The present invention relates to a novel process for preparing a .beta.-lactam derivative.
2. Prior Art
A process using ozone is widely known for preparing a .beta.-lactam derivative represented by the following formula (2) and/or the corresponding enol tautomer (which may be produced depending on its structure) from an alkenyl-substituted .beta.-lactam derivative represented by the following formula (1): ##STR3## wherein R.sup.1 is a hydrogen atom, a C.sub.1-4 alkyl group or a C.sub.1-4 haloakyl group, R.sup.2 is a hydrogen atom, a C.sub.1-4 alkyl group or a phenyl group which may have a substituent, A is a group represented by the formula ##STR4## a group represented by the formula ##STR5## or a group represented by the formula ##STR6## wherein R.sup.3 is an amino group or a protected amino group, R.sup.4 is a hydrogen atom or a group for protecting a carboxylic acid, one of R.sup.5 and R.sup.6 is a hydrogen atom and the other is either a hydroxyl group or a protected hydroxyl group, or R.sup.5 and R.sup.6, when taken together, represent an oxo group or a group represented by the formula ##STR7## wherein R.sup.7 is a hydrogen atom, a C.sub.1-4 alkyl group, a phenyl group which may have a substituent, or a group --COOR.sup.8 wherein R.sup.8 is a hydrogen atom or a C.sub.1-4 alkyl group, X is a hydrogen atom, a halogen atom, a hydroxyl group or a protected hydroxyl group, and Y is a group of the formula --SO.sub.2 Ar or --SAr wherein Ar is an aryl group which may have a substituent or a nitrogen-containing aromatic heterocyclic group which may have a substituent; and ##STR8## wherein R.sup.1 and A are as defined above (see, e.g. Japanese Unexamined Patent Publications Nos. 129590 1975 and No.98265/1976).
However, the process using ozone has the disadvantages of requiring special equipment and unavoidably producing a highly explosive ozonide as an intermediate during the ozone-oxidizing reaction, consequently involving a dangerous procedure. Another problem is that the ozone-oxidizing reaction must be conducted using ozone in the form of a dilute solution at an extremely low temperature, making it difficult to carry out the process on an industrial basis.
As described hereinbefore, the conventional processes for preparing the .beta.-lactam derivative of the formula (2) from the alkenyl-substituted .beta.-lactam derivative of the formula (1) by the oxidation of ozone are difficult to industrially practice and have various drawbacks to be overcome.
It is an object of the present invention to provide a novel process for preparing the derivative of the formula (2) and/or the corresponding enol tautomer with a high purity in a high yield from the derivative of the formula (1), the process being free of the drawbacks of the foregoing conventional processes, safe and convenient to perform and industrially fully feasible.